Tire testing machines generally involve a tire which is to be tested being rolled under a loading against the outside peripheral surface of a cylindrical testing drum. The testing speeds at which the tire is rotated are usually very high and may be over 300 kph in known tire testing machines. That in turn involves the testing drum to also rotate at a very high speed.
In the case of a construction in which the testing drum is formed by a rotor wheel assembly comprising a rotatably mounted hub, a hollow-cylindrical testing drum portion surrounding the hub, and a supporting means for supporting the testing drum portion with respect to the hub, various operational difficulties may occur. To permit such difficulties to be more readily appreciated, reference will be directed at this point to FIGS. 1 and 2 of the accompanying drawings, showing a known rotor wheel assembly for a tire testing machine. FIG. 1 shows in its left-hand half a view on to the end face of the rotor wheel assembly while the right-hand half of FIG. 1 shows a view in section taken radially through the center of the rotor wheel assembly. FIG. 2 is a view in section taken along section line A-C in FIG. 1.
In the case of the rotor wheel assembly shown in FIGS. 1 and 2, a support means disposed between the hub 32 and the testing drum portion 33 is formed by two lateral flat support discs indicated at 17 in FIG. 1, and in addition radially extending spokes 14 and ribs 15. It has been found that at high testing speeds the peripheral portion constituting the testing drum portion 33 and against the outside surface of which a tire to be tested is applied under a pressure loading experiences deformation at its contact surface in an irregular fashion due to centrifugal forces or due to the external loading applied thereto. Such deformation can be clearly seen in the right-hand half of FIG. 1, in comparison with the undeformed structure shown in the left-hand half of FIG. 1, while the upper part of FIG. 2 also shows the structure which is deformed by centrifugal force, in qualitative terms. If during a tire testing operation for testing the degree of uniformity of the tire, measurements in respect of irregularities in the forces involved in the combination of the rotor wheel assembly and the tire being tested thereagainst are made, the measurement values produced in that operation may frequently be falsified by the above-mentioned deformity of the rotor wheel assembly. A considerable amount of expenditure in terms of measuring procedure and equipment will then be required in order to provide compensation for the falsification of the measurement values produced by the assembly.